Sand consolidation



United States Patent Ofitice 3,297,089 Patented Jan. 10, 1967 3,297,089SAND CQNSOLIDATION Horace H. Spain, Houston, Tex., assignor, by meansassignments, to Esso Production Research Company, Houston, Tex., acorporation of Delaware No Drawing. Continuation of application Ser. No.191,-

409, May 1, 1962. This application Oct. 24, 1965, Ser. No. 505,051

11 Claims. (Cl. 166-33) This application is a continuation ofapplication Serial No. 191,409, entitled Sand Consolidation, filed May1, 1962, and now abandoned, which application is a con--tinuation-in-part of application Serial No. 73,535, entitled SandConsolidation, filed December 5, 1960, and now abandoned.

This invention is primarily directed to a method for consolidating thesands of loose or incompetent formations penetrated by a borehole, andin this regard the invention more particularly concerns a method forconsolidating the sands of subsurface formations by injecting into themthermosetting plastics, which set in the formations and bind the sandparticles of the formations together.

A primary object of the present invention is to provide a method of sandconsolidation that is economical, rapid acting, and generally applicableto various types of formations. Also, the method of the inventionovercomes disadvantages inherent in other sand consolidating procedures.

In producing fluids from subsurface formations, sand is produced alongwith the formation fluids from loosely consolidated formations. Varioussand control measures to inhibit or prevent sand particles from movinginto the well bore from the formations have been attempted, because sandproduction with its attendant accumulation in the well bore or movementto the surface causes serious operational problems. One manner of sandcontrol that has been tried is the use of thermosetting plastics whichset and bind the sand particles of the formation together whilepermitting flow of well fluids therethrough.

One good sand consolidating plastic makes use of the resin-formingproperties of the reaction between a watersoluble aldehyde and a lowmolecular weight hydroxy aryl compound catalyzed by an alkaline or acidcatalyst. When these compounds are injected into a sand formation, aresin forms which cements the particles of the formation together.Although any water-soluble aldehyde may be used, formaldehyde,acetaldehyde, propionaldehyde, or mixtures thereof are preferred. Thelow molecular weight hydroxy aryl compound may include phenol, cresol,beta naphthol, resorcinol, or cresylic acid, or mixtures thereof; forlow temperature formations, xylenol, especially 3,5-xylenol, ispreferred. Suitable alkaline catalysts which may be used includeguanidine salts, such as guanidine carbonate and amino-guanidinebicarbonate; alkali metal hydroxides and carbonates, such as sodiumhydroxide or sodium carbonate; aliphatic amines, such as ethyl amine andtriethyl amine; aromatic amines, such as aniline; and aliphaticdiamines, such -"as ethylene diamine. Suitable acidic catalysts whichmay be used include acidic salts, such as stannous chloride or magnesiumchloride; mineral acids, such as hydrochloric acid or sulfuric acid;acid anhydrides, such as maleic anhydride; aromatic acids, such aspicric acid or benzene sulfonic acid or sulfanilic acid; and polynucleararomatic acids or acid salts, such as alpha naphthylamine sulfonic acidor sodium-1-naphthylamine-3,6,8-trisulfonate.

It has been found that injection of the reactive ingredients of thephenolic type plastic mixture in two parts is better than injection of amixture of all of the reactive ingredients together, for in the latterprocedure, for example, base catalyzed plastics must be refrigeratedduring mixing to prevent premature separation and hardening in the tanksor tubing; acid catalyzed plastics may not be used for low temperatureformations because of the danger of slight deviation in a component ofthe composition causing premature separation; and neither the basecatalyzed nor the acid catalyzed plastics can be used to consolidateunusually long producing intervals, because the prolonged injection timerequired to consolidatesuch intervals would cause separation of theplastic mixture before placement could be completed.

in the two-part injection procedure, the first part injected includesall the reactants except the low molecular weight hydroxy aryl compound.The second part injected includes the low molecular weight hydroxy arylcompound dissolved in oil. The second part of the plastic mixture issubstantially imiscible with the first part of the mixture. Therefore,as the second part passes through the formation sand following injectionthereof, a portion of the first part remains on the sand surfaces as theconnate liquid and extracts a fraction of the low molecular weighthydroxy aryl compound from the second part. The concentration of thehydroxy aryl compound in the second injected part is so regulated thatextraction of the hydroxy aryl compound will cease when the first partinjected has dissolved the proper amount of the hydroxy aryl compound.The proper concentration of the hydroxy aryl compound in the second partof the mixture injected is experimentally determinable. Thisconcentration is dependent on the volume of solution it is desired touse, and it is the amount that will cause the sand to be consolidatedthroughout the treated portion. An excessive concentration of hydroxyaryl compound in the oil causes the sand nearest the well bore to beinadequately consolidated. Conversely, too low a concentration willconsolidate too little sand to withstand the pressure differentialcaused when the well is produced.

Another good sand consolidating plastic makes use of the resin-for mingproperties of epoxy resin solutions together with a hardener or curingsolution, as described and claimed in US. pat. appl. Serial No. 51,033,entitled Sand Consolidation, filed August 22, 1960, now Patent No.3,100,527, by Albert R. Hilton, Jr. and Horace H. Spain. The formationsand is treated with a solution of epoxy resin and an oil-alcoholsolvent followed by a large volume of viscous oi1-hardener solution, ora limited volume of viscous oil-hardener solution and a large volume oflight-oil-hardener solution. The desirable properties of chemicalinertness, high strength, and superior wetting of the epoxy resins areutilized to give an im proved sand consolidation. The epoxy resinspreferred for purposes of this application are the diglycidyl ethers ofbisphenol A [bis(4-hydroxypheno'l) dimethylmethane] obtained by thereaction between epichlorohydrin (1 chloro-2,3 epoxypropane) andbisphenol A using carefully controlled additions of caustic soda tocontrol the pH neutralizing the hydrochloric acid formed in thereaction. The pH is maintained just below the endpoint ofphenolphthalein, about 8 to 8.5. The ihardeners or accelerators havingthe property of catalyzing the reaction of the thermosetting resin atlow temperatures include amines, dibasic acids, and acid anhydrides.Typical compounds that will serve as curing agents are diethylenetriamine, diethylamino propylamine, ethylene diamine, triethylenetriamine, ditrimethylaminome-thylphenol ,(DMP-- 30, made by Rohm andHaas and the preferred catalyst), benzyldimethylamine,metaphenylenediamine, and 4,4 methylene dianiline, are typical of theamine curing agents. The acids and anhydrides are illustrated by oxalic,.phthalic, pyromel-litic dianhydride and dodecenyl succinic anhydride.

The epoxy resin is dissolved in a solvent that can also dissolve asubstantial amount of water but still have a favorable partitioncoefficient to extract the hardener from the oil solution which is laterused to displace the epoxy solution. In order that a rather highsaturation of the epoxy solution remains after immiscible displacementwith the oil-hardener solution, it is desirable that the viscosity ofthe epoxy solution be at least 3 cps. at the temperature of theformation to be treated. The viscosity would be preferably in the rangefrom 5 to 25 cps. at the formation temperature.

The preferred solvent for the epoxy is ethyl alcohol denatured withmethyl alcohol and kerosene in the range from 60 to 90 percent by volumealcohol to 40 to percent kerosene. The kerosene must contain somearomatics to give a clear, homogeneous solution suitable for use. Otheroils that may be used are diesel oil and white oil to which somearomatics, i.e., toluene, have been added. Suitable solvents other thanethyl alcohol are acetone or methyl-ethyl ketone.

The oil used for the solvent for the hardener must be substantiallyimmiscible with the alcohol-kerosene mixture, contain no aromatics, andoffer a satisfactory partition coefficient for the hardener to go intothe epoxy solution. These requirements are satisfied by an acid-treatedkerosene or diesel oil by the white oils such as Bayol D or White Oil95. White oils are specially treated, refined oils that contain nounsaturated or aromatic compounds.

The hardener solution may contain from 0.5 to 10 percent hardenerdissolved in the oil. The preferred range is from 1 to 5 percenthardener.

Typical commercial epoxy materials are:

1 Shell Chemical Co., Epon 815, is the preferred epoxy and the one withwhich the experimental work has been (lone. This composition contains anundisclosed diluent, which accounts for its high epoxide equivalent andlow viscosity.

In the sand consolidation process a solution of 50 to 100 percent epoxyresin dissolved in a solvent composed of 60 to 90 percent denaturedalcohol and 10 to 40 percent kerosene is prepared and injected into theformation.

The kerosene in this solution must contain some aromatics. A volume ofhardener in a viscous white oil, the volume of which is about equal tothe epoxy solution, then is prepared and injected into the formation.After this, about 2 to 10 volumes of a hardener kerosene solution isprepared and injected into the formation. The concentration of thehardener in the white oil and kerosene solutions preferably is in therange of 0.5 to 10 percent, and both the white oil and kerosene must befree of aromatics.

To improve the effectiveness of the phenolformaldehyde resins and theepoxy-type resins when used as sand consolidating media, it is proposedto incorporate in the solution or solutions which deposit the resin inthe formation sands, a moderate quantity of a chemical agent.

The chemical agents used for this purpose are aminofunctional organosilane compounds, typical examples of which are2,aminoethyl-aminopropyl-trimethoxy silane;2,a'minoethyl-aminopropyl-tripropylene oxide silane; 2,a'minoethyl-aminopropyl-triethylene oxide silane;2,aminomethyl-aminopropyl-trimethoxy silane;2,aminopropylaminopropyl-trimethoxy silane;1,trimethoxy-2,aminoethyl-2,aminopropyl disilane; 1,triethyleneoxide-2,aminoethyl-2,-aminopropyl disilane; 1,tripropylene oxide-2,aminoethyl-2,aminopropyl disilane;l,trimethoxy-2,aminomethyl-2,aminopropy1 disilane;l,trimethoxy-2,aminopropyl-2,aminopropyl disilane; andl,trimethoxy-2,aminoethyl-2,aminoethyl disilane.

The preferred agent is the compound 2,aminoethylaminopropyl-trimethoxysilane, which is a product manufactured and marketed by the Dow-CorningCorporation, Midland, Michigan, under the trade name Z-6020.

Experiments were performed which show improved sand consolidationsresult when an amino-functional silane is used with the sandconsolidating phenol formaldehyde and epoxy-type resins.

The following experiments illustrate the beneficial results obtainableusing an amino-functional silane with the phenol formaldehyde typeresin.

Two l-in. I.D. plastic tubes were packed with sand produced from a well.These sand-packed tubes were treated by flowing through the tubes ml. ofsalt water followed by 100 ml. of diesel oil to simulate oil sand in itsnatural condition. Through one of the tubes then was flowed a solutionconsisting of 100 ml. of commercial 37 percent formalin, 13.9 weightpercent guanidine carbonate, and 2.8 weight percent sodium hydroxide.Through the other of the tubes then was flowed the same solution,including 1 weight percent of the silane compound Z-6020. Through eachof the tubes then was flowed a solution consisting of 100 ml. of dieseloil, 1.4 gm. meta-para cresol, and 1.4 gm. of 3,5 xylenol. The two tubeswere cured in a 140 F. water bath for 16 hours. At the end of the curingperiod, samples were cut from each of the tubes and the compressivestrengths were measured. The compressive strength of the sample in thetube treated with the solution containing the compound Z6020 was 1275p.s.i., while the compressive strength of the other sample was only 427p.s.i.

The following experiments illustrate the benefits obtainable through theuse of an amino-functional silane with the epoxy resins.

Eight sand tubes were prepared and saturated to simulate an oil sandcontaining connate water. The sand in each of the tubes was treated withepoxy resin mixed in situ using 400 cc. of resin solution containing 75percent epoxy dissolved in a solvent of 75 percent denatured ethanol and25 percent kerosene, 350 cc. Humble White Oil 95 (an acid-treatedrefined oil having a viscosity of about 25 centipoises) containing 2 /2percent DMP-30, and 2000 cc. of kerosene (an acid-treated kerosene of aviscosity of about 2 centipoises). In four of the tubes, the silanecompound Z-6020 (-0.5 percent by weight) was included in the epoxysolution, and in the other four tubes it was omitted. After treatment,the tubes were cured in a water bath at F. The treatment was substantialin "volume compared with the pore volume of the sand tube in order tosimulate the effect of the flow through the sand immediately adjacentthe perforation.

The results of these experiments are given in Table I.

strength on. rate is believed due to the stripping down to low residualsaturation of the epoxy solution by the viscous drag of the hardenersolution.

In test Nos. 1, 4, 5, and 8 of Table I the tubes were treated at aboutthe same injection rate. In the case where no water contacted thetreated sand and no silane was used, test No. 4, the strength was 815p.s.i.; whereas when water contacted the sand, test No.1, the strengthwas reduced to 331 p.s.i. In contrast, the tests where the silane wasused, test Nos. 5 and 8 particularly, the strength was about 850 psi.regardless of whether water contacted the treated sand or not.

The results of an additional series of tests conducted in a mannersimilar to that described for test Nos. 1-8 are shown in Table II.

A group of tests was performed. 2 A single test was performed.

The data of Table II are similar to the data of Table I. In the group oftests A where there was no silane used and no water flush, the sandstrengths ranged from 102 to 1390 p.s.i. (dependent upon the injectionrate), whereas in the group of tests B where again no silane was used,but a water flush used, the strengths were reduced to 13 to 331 p.s.i.Also, in test C a strength of 890 p.s.i. resulted using silane and noafterfiush, and in the group of tests D strengths in the range of 357 to828 resulted using silane and the afterflush.

Although epoxy resins provide a superior sand consolidation and at thesame time avoid the hazard of the exothermic reaction often encounteredwith phenolic resins, it is seen from the data of Tables I and II thatif the epoxy resin-treated sand is contacted by water afterconsolidation of the sand, serious weakening of the consolidationtreatment results. However, these data also show that by employing anamino-functional silane in the epoxy solution, this difliculty isovercome, and a good sand consolidation results. The importance of thediscovery that the use of an amino-functional silane aids in avoidingthe loss of strength of the consolidation treatment when water contactsthe sand shortly after treatment is stressed, for many wells requiringsand consolidation produce water, and the loss of the strength oftreatment in such wells could easily cause failure.

Having fully described the nature, objects, and operation of myinvention, I claim:

1. In a method for consolidating the sands of an incompetent formationin which a resin-forming mixture is introduced into said formation intwo parts, the first part injected miscibly displacing liquid wettingthe sand grains of the formation and a portion of the first partremaining on the surface of the sand grains, and the second partinjected immiscibly partially displacing the first part injected, theportion of the first part injected remaining on the sand grain surfacesextracting a fraction of the second part injected to form the resin andthereby consolidating the sands of the formation, the improvementcomprising: including an amino-functional organo silane in one of theparts of said resin-forming mixture.

2. A method as recited in claim 1 including employing a phenol typeresin-forming mixture.

3. A method as recited in claim 2 including employing saidamino-functional silane in the range of .1 to 10' percent by weight.

4. A method as recited in claim 2 in which said first part of saidresin-forming mixture comprises an aldehyde and a catalyst and saidsecond part of said resin-forming mix ture comprises a low molecularweight hydroxy aryl compound.

5. A method as recited in claim 4 in which said silane is included insaid first part of said resin-forming mixture.

6. A method as recited in claim 5 in which said first part of saidresin-forming mixture includes an aldehyde, guanidine carbonate andsodium hydroxide and said second part of said resin-forming mixtureincludes cresol and xylenol.

7. A method as recited in claim 1 including employing an epoxy typeresin-forming mixture.

8. A method as recited in claim 7 including employing saidamino-functional organo silane in the range of .1 to 10 percent byweight.

9. A method as recited in claim 7 in which said first part of saidresin-forming mixture comprises an epoxy resin solution and said secondpart of said resin-forming mixture comprises a hardener solution.

10. A method as recited in claim 9 in which said silane is included insaid first part of said resin-forming mixture.

11. A method as recited in claim 10 in which said first part of saidresin-forming mixture includes epoxy dissolved in ethanol and keroseneand said second part of said resin-forming mixture includesditrimethyl-aminomethylphenol dissolved in oil.

References Cited by the Examiner UNITED STATES PATENTS 3,199,590 8/1965Young 166-33 T. A. ZALENSKI, S. J. NOVOSAD, Assistant Examiners.

1. IN A METHOD FOR CONSOLIDATING THE SANDS OF AN INCOMPETENT FORMATIONIN WHICH A RESIN-FORMING MIXTURE IS INTRODUCED INTO SAID FORMATION INTWO PARTS, THE FIRST PART INJECTED MISCIBLY DISPLACING LIQUID WETTINGTHE SAND GRAINS OF THE FORMATION AND A PORTION OF THE FIRST PARTREMAINING ON THE SURFACE OF THE SAND GRAINS, AND THE SECOND PARTINJECTED IMMISCIBLY PARTIALLY DISPLACING THE FIRST PART INJECTED, THEPORTION OF THE FIRST PART INJECTED REMAINING ON THE SAND GRAIN SURFACESEXTRACTING A FRACTION OF THE SECOND PART INJECTED TO FORM THE RESIN ANDTHEREBY CONSOLIDATING THE SANDS OF THE FORMATION, THE IMPROVEMENTCOMPRISING: INCLUDING AN AMINO-FUNCTIONAL ORGANO SILANE IN ONE OF THEPARTS OF SAID RESIN-FORMING MIXTURE.